Telecommunications equipment racks or bays are typically installed in controlled environment vaults, central switching offices, and remote switch buildings. Many conventional racks presently found in such facilities are large and cumbersome, because there has previously been a need to accommodate bulky and heavy equipment such as copper wiring and electromechanical switching components. The overall height of a conventional rack is typically 11.5 feet, which corresponds the ceiling height of rooms in which such racks are installed. To provide strength and stability, telecommunications racks are typically bolted to the floor and tied off the ceiling superstructure, and cables and wires are run from the superstructure directly through the tops of the racks.
Because of recent advances in the telecommunications industry, including the development and use of fiber optic transmission cable and small-scale, fully electronic components, the design of racks has been scaled down. As a result, the overall height required for racks has been reduced to 9 feet and most recently has been reduced to 7 feet. However, the ceiling heights of pre-existing facilities have not changed. New 7 foot racks may be installed next to old 9 foot or 11.5 foot racks. As a result, gaps are created between the tops of the 7 foot racks and the ceiling of the facility. This is undesirable in that wires or cables running down from the ceiling superstructure to the 7 foot racks are exposed and not protected by the racks, and the racks cannot be tied off to the ceiling superstructure with the use of conventional means. It is particularly undesirable in localities where the racks must adhere to rigid industry standards regarding the ability of telecommunications racks to withstand seismic forces. For example, racks of this type must be designed to meet the BELLCORE Zone 4 seismic test set forth in Document # GR-63-CORE.
Accordingly, there is a need for a telecommunications rack which can be adapted for installation in facilities with either 7, 9 or 11.5 foot ceilings. One way to accomplish this is to provide extension assemblies that are mountable to the top of a 7 foot rack. However, the rack with the extension assembly installed thereto must still meet industry seismic standards. In addition, the industry has recommended that users of such racks refrain from installing telecommunications equipment in the extended portions of the racks. This is because the extended portions themselves are not designed to safely protect telecommunications equipment from seismic forces. Unfortunately, in order to conserve space many users often ignore this recommendation and proceed to install sensitive equipment in the extended portions, thereby increasing the risk of severe damage to costly equipment. Therefore, there is a further need to provide an extension assembly that permits the rack to comply or remain in compliance with seismic standards while preventing the installation of equipment into the extension assembly itself. Applicant has designed a rack assembly which meets all of these requirements and which is described in detail hereinbelow.